WASHINGTON — The United States is facing a year or more without crucial satellites that provide invaluable data for predicting storm tracks, a result of years of mismanagement, lack of financing and delays in launching replacements, according to several recent official reviews.

The looming gap in satellite coverage, which some experts view as almost certain within the next few years, could result in shaky forecasts about storms like Hurricane Sandy, which is expected to hit the East Coast early next week.

The endangered satellites fly pole-to-pole orbits and cross the Equator in the afternoon, scanning the entire planet one strip at a time. Along with orbiters on other timetables, they are among the most effective tools used to pin down the paths of major storms about five days ahead.

All this week, forecasters have been relying on such satellites for almost all the data needed to narrow down what were at first widely divergent computer models of what Hurricane Sandy would do next: hit the coast, or veer away into the open ocean?

Right on schedule, the five-day models began to agree on the likeliest answer. By Friday afternoon, the storm’s center was predicted to approach Delaware on Monday and Tuesday, with powerful winds, torrential rains and dangerous tides ranging over hundreds of miles.

New York and other states declared emergencies; the Navy ordered ships to sea to avoid damage. Mayor Michael R. Bloomberg of New York City warned that no matter where or when the storm landed, the city would not escape its effects. And from the Carolinas to New England, public safety officials were urgently advising tens of millions of residents to prepare for the worst, including the possibility of historic flooding, power failures and snow.

“We cannot afford to lose any enhancement that allows us to accurately forecast any weather event coming our way,” said Craig J. Craft, commissioner of emergency management for Nassau County on Long Island, where the great hurricane of 1938 killed hundreds. On Thursday, Mr. Craft was seeking more precise forecasts for Sandy and gearing up for possible evacuations of hospitals and nursing homes, as were ordered before Tropical Storm Irene last year. “Without accurate forecasts it is hard to know when to pull that trigger,” he said.

Experts have grown increasingly alarmed in the past two years because the existing polar satellites are nearing or beyond their life expectancies, and the launch of the next replacement, known as J.P.S.S.-1, has slipped to 2017, probably too late to avoid a coverage gap of at least a year.

Prodded by lawmakers and auditors, the satellite program’s managers are just beginning to think through alternatives when the gap occurs, but these are unlikely to avoid it.

In response, top Commerce and NOAA officials on Sept. 18 ordered what they called an urgent restructuring — just the latest overhaul of the troubled program. They streamlined the management, said they would fill major vacancies quickly and demanded immediate reports on how the agency planned to cope with the gap. They have moved quickly to nail down the specific designs of the J.P.S.S.-1’s components, many of them already partly built. And they promised to quickly complete a new independent cost estimate to verify the program’s budget.

Ciaran Clayton, NOAA’s communications director, said in a statement that the agency’s top priority was to provide timely, accurate forecasts to protect the public, and that it would continue to develop and update plans to cover any potential gap.

The under secretary of commerce responsible for NOAA, Jane Lubchenco, issued the memorandum ordering the changes. In it, she wrote that the administration had been trying all along to fix “this dysfunctional program that had become a national embarrassment due to chronic management problems.”

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“It is a long, sad history,” said Dennis Hartmann, the chairman of a broad review of earth-observing satellite programs released in May by the National Research Council. The report projected a dismal decline in what has been a crown jewel of modern earth and atmospheric science.

The Joint Polar Satellite System also includes important sensors for studying the global climate, and these too are at risk.

But its main satellites are most notable because they put instruments to sense atmospheric moisture, temperature and the like into what is known as the “polar p.m.” orbit, a passage from lower altitude that provides sharp and frequent images of global weather patterns. (Other satellites stare continuously at one part of the globe from farther off, for short-term forecasting.)

Polar satellites provide 84 percent of the data used in the main American computer model tracking Hurricane Sandy.

For years, as the accuracy of this kind of forecasting has steadily improved, NOAA’s p.m. polar satellites have been a crucial factor, like the center on a basketball team.

But all the while, despite many warnings, the coverage gap has grown ever more likely.

The department told Congress this summer that it could not come up with any way to launch J.P.S.S.-1 any sooner. Kathryn D. Sullivan, assistant secretary of commerce, said it would “endeavor to maintain the launch date as much as practicable.”

The Government Accountability Office, which views a gap as “almost certain,” has been urging NOAA to come up with alternatives, like leaning on other commercial, military or government satellites for helpful data. But it said it would take a long time and more money to get any such jury-rigged system running.

For now, the agency is running on a stopgap bill that allows it to redirect money from other projects to the polar satellites. In approving it, Congress demanded a plan by next week showing how NOAA intended to stay on schedule and within a strict limit — about $900 million a year.

“NOAA does not have a policy to effect consistent and reliable cost estimates,” the Commerce inspector general said. The outside review team said it could not tell “if the current $12.9 billion is high, low, or exactly correct.”

The program’s problems began a decade ago with an effort to merge military and civilian weather satellites into a single project. After its cost doubled and its schedule slipped five years, that project was sundered by the Obama administration.

As its existing satellites aged and the delays mounted, NOAA finally put a new model named Suomi into orbit a year ago that now helps bridge the gap until the next launchings, in 2017 and in 2022 — two and four years late, respectively.

But there are lingering concerns that technical glitches have shortened Suomi’s useful lifetime, perhaps to just three years. Predicting a satellite’s lifetime is like trying to guess when a light bulb will go out. The most likely timing of a gap in coverage is between 2016 and 2018, according to the best official estimates.

That would “threaten life and property,” the independent review team warned.

Correction: October 29, 2012

An earlier version of this article misstated the name of one of the government agencies running the project. It is the National Oceanic and Atmospheric Administration, not the National Oceanic and Atmospheric Agency.

A version of this article appears in print on October 27, 2012, on Page A1 of the New York edition with the headline: Satellite Plans Falter, Risking Data on Storms. Order Reprints|Today's Paper|Subscribe